iszero_jaxarray needs a default value for tol

[BoxiLi]

The rendering of qutip matrix in IPython fails

qutip.sigmax().to("jax").__str__()

with the error

TypeError: iszero_jaxarray() missing 1 required positional argument: 'tol'

I think the definition of iszero_jaxarray needs a default value for tol, e.g.

iszero_jaxarray(matrix, tol=None)